We don't have the capability to choose the latest version of the plugin (if there are multiple versions) while selecting the plugin from pipeline studio. UI defaults to the first artifact (from the list of artifacts) returned by the backend.
https://github.com/cdapio/cdap/blob/develop/cdap-ui/app/cdap/services/VersionRange/VersionUtilities.js#L19 We can use this utility to select the latest version from a list of version we have in UI.
UI now adds the latest version of plugin, among the list of different versions of the plugin, when added from the sidepanel in pipeline studio. If the user has already chosen a specific version (older version) it defaults to that instead of the latest.